It is known from commonly owned patent application Ser. Nos. 555,471 and 568,610 filed respectively by W. Bongard et al and F. Kleefeldt on Nov. 28, 1983 and Jan. 6, 1984 (now U.S. Pat. Nos. 4,596,985 and 4,686,529, respectively) and from German patent document No. 3,224,049 to control a door lock, typically of a central lock system, by means of a door-signal receiver and a decoder that unlock the lock when the receiver receives an appropriately encoded signal. A hand-held transmitter, typically a miniaturized device carried on the user's key chain, can generate the appropriately encoded door signal, so that no external or mechanical door lock need be provided, making the vehicle very secure.
In addition the motor vehicle has a drive for propelling the vehicle and a drive or ignition switch operable only by a drive key to energize the various devices--electric fuel pump, ignition system, injectors--that make the drive work by means of the vehicle's wiring. Thus the drive can only be powered when this switch is operated by the key inserted into it. Typically this ignition switch is a standard mechanical switch operated by a bitted key and provided on the steering column so this key can also operate a steering lock that physically arrests the steering wheel and prevents the vehicle, even if hot-wired, from being steered.
Thus the driver uses the radio key to get into his or her vehicle, and then employs a standard key to unlock the wheel and operate the drive system. The ignition key can be left, for instance, with a parking attendant, that is in a situation where the vehicle need not be locked, so that the owner maintains a high level of security, which is typically increased by means of the coded radio-frequency door signal.
Some problems have arisen with the use of steering-column locks. They can get jammed and become impossible to unlock without dismantling the steering column, and they can lock up while the vehicle is moving and thereby create a considerable hazard. Furthermore a skilled thief who does gain entry to the vehicle can normally rip out the lock cylinder so as to be able to unlock the steering column and actuate the drive system directly with a screwdriver twisted in the empty lock sleeve. Also, it is possible to hot wire the engine and start it without actuation of the ignition switch, provided of course somehow the steering-column lock is not a problem, a problem not overcome by replacing the mechanical drive lock with a radio-type remote-control one like the one operating the lock system.
In the above-cited copending parent application a security system is described which has, as is known, a drive for propelling the vehicle and including a drive element which must be enabled for the drive system to function. A drive switch operable only by a drive key is connected by wiring to the drive and the element thereof for enabling the element and powering the drive when the switch is operated by the key inserted into it. The door-lock system includes a door-signal receiver, and decoder, and a door lock for unlocking the lock when the receiver receives an appropriately encoded signal. A transmitter can generate the appropriately encoded door signal. According to this earlier invention the transmitter is the key and is capable of transmitting an appropriately encoded drive signal, the drive switch includes a drive-signal receiver, and a decoder is connected between the drive-signal receiver and the element for enabling same only when the appropriately encoded drive signal is received by the drive-signal receiver.
Thus according to the previous invention the same radio-frequency transmitter is used both to remotely open the door locks, and to get the car going once inside it. Both the lock system and the drive are therefore operated by respective decoders and electronic circuits which can rely on exotic codings as described in the above-mentioned patent, making the keys virtually impossible to reproduce or replicate. In addition the system enables a drive device that can be any part critical to the operation of the drive, as for instance a relay or gate in the ignition system, a valve in a fuel pump, or a gate at any of a dozen locations in the drive. The radio-frequency signal is directed through the vehicle wiring to the decoder and cutout device somewhere in the drive, so that a clever thief who attempts to hot wire this device must find it first. Since it can be made small enough to be effectively hidden and/or encapsulated in a standard part, it can be made very small to make hot-wiring the car so very difficult that a steering-column lock becomes unnecessary.
The drive signal and receiver in my earlier system are such that the drive signal can only be received by the drive-signal receiver when the transmitter is inserted in the lock. This can be done by shielding the drive-signal receiver or making the receiver for it so very insensitive that it can only receive the signal from immediately adjacent the transmitter. Since cracking the code is virtually impossible, such a key can freely be left with someone like a repair person who must operate the car. Normally the drive and door signals are the same, or are selected from the same sequences.
Typically the critical drive device according to the earlier invention is mainly operated by another power source, such as the vehicle battery. The decoder and controller serve merely to disable and enable it, not to operate it; once enabled by the decoder, the critical drive device remains on even if the signal is no longer sent.
The switch, in order to operate in the rotary fashion of a standard ignition or drive switch has a rotary cylinder shaped complimentarily to the transmitter key and including mechanical switches connected between the battery and the drive. Thus from outside the vehicle the user merely points the transmitter at the door-signal receiver, but once inside he or she inserts it into the dashboard and turns it in the standard manner, that is through a small arc to the right for the on position and full right for start. The drive is shut off in the standard manner by turning the key to the left and withdrawing it. The only difference is that when the key is put into the lock its transmitter must be actuated, normally according to the instant invention by depressing a button on the side of the key.
This arrangement is relatively efficient, but still lacks some features. For instance, even though a steering wheel lock becomes less essential due to the difficulty of starting or operating the vehicle without the proper electronic key, the system does not prevent the vehicle from being tampered with and even forcibly moved. For instance the car can be towed without difficulty, or can be pushed away since the steering remains operational.
U.S. Pat. No. 4,438,426 of Adkins describes a system wherein an automobile ignition key can emit a coded signal which, if recognized by a decoding circuit inside the lock, allows the vehicle to be operated. U.S. Pat. No. 4,250,533 of Nelson integrates the receiver and decoder, albeit using a transmitted signal, and gives the electronic key also mechanical functions. These arrangements are not suitable for use in a vehicle having a remotely operated lock system, instead the door and ignition locks are substantially identically constructed both mechanically and electronically.
German patent document No. 3,005,890 has a standard mechanical key also equipped with a transmitter capable of emitting a coded signal. Thus the locks are mainly mechanical, with the electronic coded function a simple add-on for extra security. They cannot work with a remotely operable door-lock system of the type described in above-mentioned German patent document No. 3,244,049 which requires a separate door and ignition key.
None of the described systems can also work on a column lock that prevents the vehicle from being steered when not unlocked by a proper key. Even with the most complex electronic systems, the combined functions of locking the steering wheel, operating the ignition/starting system, and unlocking the doors are never unified and controllable from a single key.